a) Field of the Invention
The present invention relates to a connection between a high voltage terminal and a ark plug head and more particularly to a spark plug connector comprising a multi-point contact system having an increased spring force interface, a compact packaging system, and reduced parts.
b) Description of Related Art
Electrical connections between a high voltage terminal and a spark plug head are well known in the art. Typically, a high voltage lead wire extends from a central high voltage source coil assembly. The lead wire contains a high voltage metal sheath with an insulating coating. The metal conductor sheath is connected to a connector usually formed of stamped sheet metal which forms an encircling clamp that snaps onto the spark plug head. An insulating boot is also provided to cover the connection between the high voltage lead wire and the spark plug. This arrangement does not provide any tolerance when assembling the connection. The resilient insulating boot must be sufficiently disposed over the spark plug before the connection can be made with the spark plug head. Furthermore, these prior art arrangements often result in the disconnection between the clamp and metal sheath when the lead wire is disconnected from the spark plug.
It is also know to employ a spring within an electrical connection of a spark plug head. However, prior art connections employing springs are complex, costly, and do not reliably provide a positive attachment of the spring to the high voltage terminal. Moreover, the prior art devices require complicated techniques and specialized tools to assemble.
Several prior art spark plug springs are being used in ignition coil applications. Most of the conventional designs use a helical compression spring to make the contact between the coil and the spark plug. Some of the conventional designs use a c-spring to make contact and also retain the high voltage lead along with the boot to the spark plug. Such a contact has a cylindrical cavity that contains the tip of the spark plug and a leaf spring in a c-shape that ensures a permanent contact to the spark plug and also retains the spark plug wire or the coil on the spark plug.
The need exists for an improved connector between the spark plug and the high voltage terminal, whereby the connector system is more compact, allows some tolerance on the location of the spark plug with respect to the engine well, and allows high spring retention to improve the connector interface.
To solve problems inherent in the prior art, the present invention provides a unique, yet simplified design for an electrical connection between a spark plug head and a high voltage terminal facilitating easy assembly.
To achieving the objectives and improved structure of the present invention, an electrical connection comprises a resilient three-point contact spring formed as a three part leaf-spring connector that snaps over the spark plug head. A case member biases the contact spring into a positive engagement working position.
With the structural arrangement of this invention, the tip of the spark plug is pinched or contacted from three directions that are spaced apart by 120 degrees. The leaf-springs do not take up space axially, therefore the package is more compact. By providing three contact points along with a higher spring load, there is a higher chance of maintaining a permanent contact between the spark plug and the high voltage terminal. In addition, the high spring retention system offers the possibility of eliminating the use of a bracket, the need for a mounting boss on the cam cover, the use of a bolt, and eliminates one operation in the engine assembly plant. Moreover, the proposed inventive design will allow radial flexibility on the location of the coil or the spark plug wire with respect to the tip of the spark plug.
In the preferred embodiment, the three part leaf-spring member of this invention is a stamped part, where a brass or zinc contact is a cast part that is followed by a secondary operation to remove burrs from the surfaces that contacts the spring.
Other objectives and features of the invention will become apparent from the following description.